gavztheouch

This makes a lot of sense. Wish I had a nice simple roof with no dormers.

Thanks, this is what I had in mind about. I did have an additional membrane over the sarking boards but I see how this is not helping. Vmzinc have a detail for this and they do not have a membrane over their sarking board but they do over the plywood. I agree I would not use standing seam again. My biggest dislike is the hard to repair factor. I have 4 flat roof dormer windows that will no doubt leak at some point, could be a nightmare waiting to happen

Im about to start building my ventilated deck. I prefer to handle sarking board vs large sheets of 18mm plywood. I noticed Vmzinc say you can use sarking board under their Zinc. Just wanted to know if anyone has used this method. How did it go? Are there any disadvantages? Some advantages I can think of are. 1. increased ventilation behind the Zinc. 2. About half the cost of Marine plywood, the best ply option, Still slightly cheaper than acceptable plywood. 3. No risk of delaminating 4. May be more forgiving if your 600mm rafter centres are not perfect. You could cut the wood back to the next rafter. Im not sure about this one. 5. Easier to see rafters to nail. 6. May be possible to do the job myself or with a little help from my dad. Disadavantages. 1. Wood thickness may vary a lot board to board. 2. The boards ends may split easier than ply 3. Less coverage per board and potentially more cutting/measuring 4. Badly warped/cupped boards may need to be discarded. Some boards may warp on the roof. Do I need to double nail each joist to stop them coming up as they dry?

EcoCocons Panels look good. This house was built with them https://www.passivhaustrust.org.uk/projects/detail/?cId=88

Yes I will be tapping the membrane to the foundation upstand. The folded up dpm or any extra bits of tape and membrane were meant to be extra barriers. Now that I have thought about it more I will revert back to the original detail of using just the membrane to stop the water getting through to the sole plate. Like you say keep it simple and try and do it well. Maybe I will monitor some choice points of the wall in times of windy wet weather to see if I can see any water getting through. An ideal solution would be a wire or some type of detector that could detect water at the sole plate. Then we would know to fix the membranes/window taping

Which option did you go for in the end?

I really like this idea but now I'm not sure I should do it. My concern is if any water finds it way to the bottom of the wall, the external membrane is trapping the water from getting out as it is taped to the upstand. There is however a possible path out as the gaps between the isoquick as quite large, some almost 10mm. These could work pretty nice as drains. If I put the tape marked in orange this will bridge over the gaps and stop the water. My next though was keeping these drains clear. I think I might have to prime the cut edge of the wood fibre board and run a length of pro clima 100mm wide vana tape over the edge to stop all the fluffy bits of wood coming off and washing down into the drain.

@Iceverge Im about to start adding the external wood fibre to my build. Im interested to hear if you still think stapling the dpm to the wall is a bad idea? I should clarify the dpm will be folded up against the racking board which is behind the wood fibre so it would need to get in between the wood fibre and the racking board which I guess would be possible. To prevent it diverting any water towards the sole plate I was planning on adding some pro clima tape to hold it against the racking board making it even more unlikely to divert water into the wall. If I could go back in time I would have maybe stapled it against the studs as this would be very unlikely to have water running down the studs. I didn't do this as the nails for the racking board would go through the dpm.

Currently leaning toward these Modified PU liquid rubber roofs. A very similar method to GRP but less sensitive to rain and temp during install and flexible once set. Looks like a better option than GRP. https://www.bmigroup.com/uk/ultima/

Many thanks Kelvin, Yes it seems flat roofer are hard to find and most people don't speak highly of their work. Ive been training myself to weld various single ply membranes but I would be able to buy most weldable single ply membrane made of stuff like PVC unless I do a course. I would be willing to do the course if they will let me.

Hi @Kelvin did you manage to find a Scottish installer?

157.414_DormerDetail.pdf Just received the details from the architect. First thoughts are it is very complicated for 4 very small dormer roofs and will be a lot of work. I don’t think the circular outlet has enough area around it to weld/glue too. There are also a lot of varying surfaces/angles and junctions in a small space. It’s annoying details like this are taken through the simplest part of the roof and do not take into consideration the more complicated areas like the upstand corners transitioning into the top of the upstand area. The upstand corners need to be detailed with a pigs ear or a remolded epdm piece this would be right in the way of the outlet. Then we have the issue of the area in the video where the pitched/flat and in upstand meet. A lot of these issues could be solved with grp. How does glass fibre cope with movement?

157.414_DormerDetail.pdf

Having a go at this in resitrix epdm. I think I need to cover both upstands in one go across the whole width of the dormer. Maybe GRP is the way forward, getting it dry enough at this time of year for GRP could be an issue. I try again with the resitrix and see if I can get it better.

This is a hard one to explain with just words. So I made a model to represent the problem. This flat roof dormer connects to a 35 degree roof clad in metal. I am having a hard time work out how to waterproof the area where the upstand for the parapet meets the sloping roof. Open to changing the roof material and design. Would much rather not have these flat roof dormers but I am here now and need to make the best job I can. World appreciate any ideas and thoughts